Oxygen heater, hot oxygen lance having an oxygen heater and pulverized solid fuel burner

ABSTRACT

There is disclosed an oxygen heater, which uses a part of supplied oxygen as auxiliary combustion oxygen, a hot oxygen lance and a pulverized solid fuel burner, both having oxygen heaters. The oxygen heater (1) has a combustion chamber (4) for both mixing and burning fuel with the part of the supplied oxygen. An oxygen-jetting opening (8) is disposed around the combustion chamber. The oxygen jetted out of the opening forms a gas curtain between an internal wall (2) and a flame (10) produced in the combustion chamber, and is heated by the flame. Both the oxygen lance and the burner includes the above-mentioned oxygen heater.

TECHNICAL FIELD

This invention relates to an oxygen heater for producing hot oxygenwhich is required in the refining of ferrous and nonferrous metals, suchas the direct reducing smelting of aluminum.

This invention also relates to a lance for supplying hot oxygen to azone for the refining of ferrous and nonferrous metals such as, inparticular, the reduction reduction zone of a direct reducing furnace.

This invention further relates to a pulverized solid fuel burner used inan electric furnace for melting steel scrap, aluminum, copper and thelike.

BACKGROUND ART

Recently, there have been developed, methods of refining aluminum in ablast furnace. In the conventional methods, such as disclosed in U.S.Pat. No. 3,661,561, oxygen preheated to approximately 1,000° C. is blowninto a blast furnace through a plurality of tuyeres of the furnace. Inthese processes, in order for the refining of aluminum in the blastfurnace to be successful, it has been important subject how efficientlythe preheated oxygen was generated and supplied to the furnace. One ofthe prior heater devices used in an experiment produced the hot oxygenby effecting the heat exchange between oxygen of room temperature and afluid generated by another heat source. However, in the experiment usingthis particular heater device, the amount of the produced hot oxygen wasseveral tens of thousand Nm³ /h. Consequently, it is not economical toapply the above-mentioned way of preheating oxygen to the preheatingprocess when there is no utilizable heat source and when a specific heatsource must be newly prepared.

Also, the use of hot oxygen in the refining process of steel or zinc,has been suggested. It is desired in this case to provide a device thatcan produce and supply a great amount of hot oxygen safely andefficiently.

In the refining of iron or aluminum, air or oxygen-enriched air issupplied to a furnace through the tuyere or the lance of the furnaceafter it is heated up to a high temperature. An example of the heaterwhich is applicable to this refining is shown in Japanese PublishedUnexamined Patent Application No. 59-501278. This heater, i.e., a burnerwhich also serves as a lance is used for heating metal products in afusion furnace. Oxygen is discharged in a jet from the nozzle of theburner and fuel is supplied from the conduit concentrically surroundingthe nozzle. The supplied fuel is then jetted into the discharged oxygenand is burned with the oxygen, which produces hot oxygen includingcombustion gas. Depending on the purpose, the oxygen content of thecombustion gas is controlled and the heater is used either as a burneror as a lance for hot oxygen containing combustion gas.

However, there arises a problem of the temperature of the peripheralportion of the burner rising severely since the construction of theburner is such that fuel supplied from the nozzle-surrounding conduit isjetted into and mixed with the oxygen flow and is burned within theburner so that the hot combustion gas including oxygen is produced.

These days, there are used, burners which utilize pulverized coal astheir main fuel for the purpose of melting steel scrap, aluminum, copperand the like. These burners must produce flames having stabletemperatures of not less than approximately 2,000° C. so that theburners have the required melting capacity. However, the combustion rateof pulverized coal is extremely slow in comparison with that of a liquidfuel such as fuel oil or a gaseous fuel such as CH₄, C₃ H₈ and the like.Also, the flame temperature of pulverized coal is lower than that of theliquid or gaseous fuel. It is not easy to produce a stable flame by themonofuel combustion of pulverized coal. The flame due to the monofuelcombustion is unstable and sometimes extinguished when the temperatureof the atmosphere in the vicinity of the burner in a furnace is low,causing its radiant heat to be reduced. For these reasons, there havebeen used, burners which utilize a gaseous or liquid fuel such as LPG,natural gas, fuel oil and the like, and the pulverized coal has beenused as the fuel of combination burners which also use a liquid orgaseous fuel along with the pulverized coal. However, the combinationburners are not economical enough since the mixture ratio of liquid orgaseous fuel must be increased, that is, the consumption of thepulverized coal must be decreased in order for the combination burnersto produce flames of high temperature.

FIG. 1 shows an instance of the conventional combination burner whichuses pulverized coal mixed with a liquid fuel. This burner has sixcylinders coaxially disposed to each other, wherein the innermostcylinder is a conduit 231 for supplying liquid fuel, the cylindersurrounding the conduit 231 is a conduit 232 for supplying auxiliarycombustion gas for assisting the combustion of the liquid fuel, thecylinder surrounding the conduit 232 is a conduit 233 for supplyingpulverized coal, the cylinder surrounding the conduit 233 is a conduit234 for supplying auxiliary combustion gas for assisting the combustionof the pulverized coal, and the last cylinder surrounding the conduit234 is a jacket 235 for circulating cooling water. The liquidfuel-supplying conduit 231 is provided at its front end with a nozzle236 for discharging the liquid fuel supplied through the conduit 231 ina jet. Also, the auxiliary combustion gas-supplying conduit 232 isprovided at its front end with a ring 237 which forms the nozzle fordischarging the auxiliary combustion gas in a jet. The auxiliarycombustion gas is jetted from the annular opening 238 defined by boththe outer periphery of the nozzle 236 and the ring 237, and is mixedwith the liquid fuel to produce a primary flame. Reference numeral 239denotes a cylinder which defines a main combustion chamber 240 incooperation with the liquid fuel nozzle 236, the front end of theauxiliary combustion gas-supplying conduit 232 and the front end of thepulverized coal-supplying conduit 233. The rear end of the maincombustion chamber 240 is in fluid communication with an outlet 241 ofthe pulverized coal-supplying conduit 233. Around the outlet 241, anoutlet 242 for jetting a part of auxiliary combustion gas is open and isin communication with the rear end of the main combustion chamber 240.The pulverized coal discharged from the outlet 241 is mixed with theauxiliary combustion gas discharged from the outlet 242 and is burned bythe assistance of the primary flame by the liquid fuel, producing asecondary flame. In front of the combustion chamber 240, asub-combustion chamber 243 is defined by the inner face of the auxiliarycombustion gas-supplying conduit 234 and the front face of maincombustion chamber 240. The remainder of the auxiliary combustion gas isjetted into the sub-combustion chamber 243 through the space between thecylinder 239 and the conduit 234, and surrounds the primary andsecondary flames to achieve a perfect combustion. In short, in theconventional burners, the flame produced by the liquid fuel and theflame produced by the pulverized coal are combined and form a unitaryflame.

As has been described, although it has been planned and tested theblowing of hot oxygen into smelting furnaces upon refining ferrous andnonferrous metals, there has been no oxygen heater, so far, which canefficiently heat an extremely large quantity of oxygen without severelylowering the purity of the oxygen and which is concerned about thesafety and durability of itself during the heating process.

Also, the conventional burner uses an unnecessarily large amount of fuelsince the hot combustion gas in the vicinity of the burner is cooled bythe cooling water circulating in the jacket of the burner, increasingthe heat loss. As a result, there arises a problem of the oxygen contentof the combustion gas being decreased. That is, the decrease of theoxygen content is not desirable upon the refining of ferrous andnonferrous metals such as, in particular, the fused reduction ofaluminum.

Furthermore, there has existed no monofuel combustion burner, for use ina furnace such as an electric furnace for steel scrap, fusion furnacefor aluminum and a reverberatory furnace for copper, which is capable ofproducing a stable flame of high temperature and has a excellent fusingability even if it is used at regions in the furnaces where thetemperature of the atmosphere in the vicinity of burner is relativelylow.

The present invention is proposed regarding the above-mentionedsituation. An object of the present invention is to provide an oxygenheater which is capable of heating a large quantity of oxygenefficiently without severely lowering the purity of oxygen and which isconcerned about the safety and durability of itself during the heatingprocess.

Another object of the present invention is to provide an oxygen lancehaving an oxygen heater which has a compact construction and reduces theheat loss such as, in particular, the heat loss in the combustiongas-producing region, thereby producing hot gas having a high oxygencontent.

A further object of the present invention is to provide a pulverizedsolid fuel burner in which the pulverized solid fuel is used as the mainfuel and gaseous or liquid fuel is used merely for preheating auxiliarycombustion gas.

DISCLOSURE OF THE INVENTION

With these objects in view, one aspect of the present invention isdirected to an oxygen heater having a combustion chamber and anoxygen-jetting opening formed in the wall defining the combustionchamber. In the combustion chamber, fuel is mixed with oxygen and burnedwith the oxygen. The opening is disposed around the combustion chamberso that the oxygen jetted out of the opening forms a gas curtain betweenthe internal wall and the flame produced in the combustion chamber. Inthis oxygen heater, a part of the supplied oxygen is used as anauxiliary combustion gas, whereby the remainder of the supplied oxygenis heated up.

The oxygen-jetting opening may comprise a plurality of nozzles or one ormore slits. The opening may be arranged so that the oxygen jetted out ofthe opening forms a multilayer of gas curtains Also, in this case, theopening may be arranged so that the flow rate of an inner gas curtain islarger than that of an outer gas curtain.

In case that the internal wall is made of a metal, the internal wall maybe provided at its outer face with a heat-insulating layer and/or acooling jacket.

The aforementioned fuel may be gaseous or liquid fuel. The fuel-jettingopening must be the proper one needed for the type of fuel used for theheater.

The oxygen used for the heater is usual industrial oxygen having apurity of 99.8%. Naturally, oxygen produced by a PSA, having a purity of90%, is also applicable to the heater.

The operation of the oxygen heater will now be described.

A part of the supplied oxygen together with the fuel, is introduced intothe combustion chamber. Then, the mixture of the fuel and the oxygen isburned, whereby a stable flame is blown out of the opening of thecombustion chamber. Most of the remainder of the oxygen, which is to beheated up, is jetted out of the nozzles or slits for forming the oxygencurtain surrounding the produced flame. The oxygen curtain prevents theinternal wall both from being local overheated and from unnecessarilyreleasing heat, thereby protecting both the internal wall made of metaland the internal wall made of refractory material.

Also, the curtain oxygen cools not only a chamber-forming member whichdefines the oxygen-jetting opening but also the combustion chamber. Thecurtain oxygen is mixed in front of the combustion chamber with thecombustion gas that is produced in the combustion chamber to beoxygen-containing hot gas, and the hot gas is supplied to the placewhere it is demanded. The maximum temperature of the hot gas at theoutlet of the heater is equal to the temperature of a perfect mixture ofthe combustion gas and oxygen having room temperature. When thetemperature of the hot gas at the outlet is approximately 700° to 1,000°C., there is no need for the cooling jacket surrounding the internalmetal wall since the oxygen curtain protect this internal metal wall.When the temperature of the hot gas increases to 1,200° C. and over,cooling means such as a cooling jacket for cooling the metal internalwall must be provided.

The preferable cooling means are, to arrange a multilayer of oxygencurtains This results in a stable streamline flow of curtain oxygenprotecting the internal wall more effectively. In this case, by makingthe flow rate of an inner curtain oxygen higher than that of the outercurtain oxygen, the outer oxygen curtain adjoined to the internal wallis retained more successfully and protects the the internal wallcompletely.

Although the oxygen heater according to the present invention isproposed as a heater for supplying a great amount of hot oxygen forsmelting, its use is also naturally applicable to other objects whichrequire hot oxygen.

According to the oxygen heater of the present invention, a great amountof hot oxygen for refining can be produced efficiently by using littlefuel for heat source. Also, the heater of the present invention preventsthe internal wall from being local overheated, thereby enhancing thesafety and durability of the heater itself both when the internal wallis made of metal and when the internal wall is made of refractory.Furthermore, this total apparatus is capable of being compact.

Since, in this heater, heat loss from the internal wall to outside theheater is minimized, the amount of the fuel used for heating oxygen isreduced, whereby there is produced, hot gas having a high oxygen contenteven though this hot gas has a relatively high temperature.

Another aspect of the present invention is directed to a hot oxygenlance having an outer cylinder in which an oxygen heater, having acombustion chamber and a oxygen nozzle, is disposed. In the combustionchamber, fuel is mixed with oxygen and is burned with the oxygen. Theoxygen nozzle directs the oxygen passing therethrough to form an oxygencurtain surrounding the combustion chamber. A heat-insulating layerand/or a cooling jacket may be disposed around a part of, or the entire,outer cylinder. Also, the lance may have a center pipe around which aplurality of the combustion chambers, in which the fuel is mixed andburned with oxygen, are provided. The oxygen nozzle may be arranged sothat a multilayer of oxygen curtains coaxial to one another are formed.In this case, it is preferred to arrange the oxygen nozzle so that theflow rate of an outer oxygen curtain is higher than that of an inneroxygen curtain.

It is also preferred that the fuel used for the lance is gaseous orliquid fuel.

Furthermore, the outer cylinder may have a branch cylinder in which theoxygen heater is disposed. The oxygen nozzle for forming the oxygencurtain may be a plurality of small holes or a slit.

The operation of this oxygen lance is as follows: In the oxygen lanceaccording to the present invention, a part of the supplied oxygen isintroduced into the combustion chamber together with the gaseous orliquid fuel, and is mixed with the fuel. The fuel is, then, burned withthe oxygen and produces a stable flame which blows out from the frontopening of the combustion chamber. The remainder of the oxygen, that is,most of the supplied oxygen that is to be heated up is blown out of thesmall holes or the slit along the inner surface of the outer cylinder,resulting in the formation of the oxygen curtain. The oxygen curtainprevents the outer cylinder from local overheating and reduces the heatradiation from the outer cylinder. In other words, by making oxygen ofroom temperature flow between the flame and the outer cylinder, theouter cylinder is protected from the heat and the heat loss from theouter cylinder is reduced and fuel consumption is lowered. Therefore,oxygen-containing gas having a high oxygen content and a hightemperature is produced. This oxygen curtain also cools the oxygenheater (that is, a burner nozzle) which constitutes the combustionchamber. Furthermore, the oxygen lance may be provided at its centerposition with a center pipe either for supplying pulverized material orfor observing the inside of a furnace. A plurality of the combustionchambers may be disposed circumferentially around the center pipe. Inthis case, the oxygen curtain should be formed so as to enclose each ofthe combustion chambers, whereby both the center pipe and the outercylinder are prevented from being overheated and the heat radiation fromboth the center pipe and the outer cylinder is reduced. Consequently,the fuel consumption of the lance is lowered and the oxygen-containinggas having a high temperature and a high oxygen content is produced.

The combustion gas produced in the combustion chamber is mixed with thecurtain oxygen in front of the combustion chamber and is jetted out ofthe front opening of the outer cylinder Thus, the maximum temperature ofthe mixed hot gas in contact with the outer cylinder is equal to thetemperature of complete mixture of the combustion gas and oxygen at roomtemperature. When the temperature of the hot gas jetted out of the frontopening of the lance is approximately 700° to 1,000° C., the coolingjacket as means for protecting the outer cylinder is not necessary sincethe oxygen curtain is capable of cooling the outer cylinder efficiently.However, when the temperature of the produced hot gas exceeds 1,200° C.,the cooling jacket and the like is necessary for protecting the metalouter cylinder

It is preferred to arrange the oxygen curtains in multilayer in order tomake the streamline flow of the oxygen stable, causing the outercylinder to be protected effectively. By increasing the flow rate of aninner curtain oxygen higher than that of an outer curtain oxygen, theouter oxygen curtain is retained stably, whereby the outer cylinder isboth protected from heat and prevented from releasing heat almostperfectly. In the same and almost perfect manner, the center pipe isboth protected from heat and prevented from releasing heat in case ofthe lance having the center pipe.

In the hot oxygen lance of the present invention, gaseous or liquid fueland auxiliary combustion oxygen are introduced into the combustionchamber and are burned to produce a flame. The combustion gas due to theflame and oxygen is mixed so that oxygen-containing hot gas is produced.Since the lance has an oxygen heater in which is included an oxygennozzle for forming oxygen curtain which encloses the combustion chamber,it is possible to protect the outer cylinder and to reduce the heat lossfrom the outer cylinder to a minimal level.

In case that the lance is provided at its center position either with apulverized material-supplying conduit or with a conduit for observation,a plurality of the combustion chambers are circumferentially disposedaround the center pipe so that there are produced oxygen curtainsenclosing the combustion chambers, whereby both the outer cylinder andthe center pipe are protected and the heat loss is decreased to aminimal level. Consequently, with a small amount of fuel capable ofraising the temperature of oxygen, hot combustion gas having a highoxygen content can be produced. Also, when the temperature of the hotgas blown out of the jetting opening of the lance is approximately 700°to 1,000° C., means for cooling the outer cylinder, such as the coolingjacket can be omitted.

Still another aspect of the present invention is directed to apulverized solid fuel burner having a burner body and an auxiliarycombustion gas heater. The auxiliary combustion gas heater produces hotauxiliary combustion gas by mixing and burning gaseous or liquid fuelwith a part of the supplied auxiliary combustion gas and, by mixing thecombustion gas which results from the combustion of the fuel with therest of the auxiliary combustion gas which is to be used for burningpulverized solid fuel. The pulverized solid fuel may be preheated due tothe heat transfer from the hot auxiliary combustion gas, and then, maybe mixed and burned with the hot auxiliary combustion gas. Furthermore,the burner may have a main combustion chamber in which the pulverizedsolid fuel is both mixed and burned with the hot auxiliary combustiongas. The auxiliary combustion gas may comprise oxygen, oxygen-enrichedair or air. Also, heat-insulating layers may be disposed on that portionof the burner body where the auxiliary combustion gas heater is attachedand on that portion of the burner body which the hot auxiliarycombustion gas is brought into contact with. The cooling jacket throughwhich cooling water circulates may be circumferentially provided on theouter surface of the burner body.

The operation of the burner according to the present invention isdescribed as follows: In the auxiliary combustion gas heater, gaseousfuel such as propane and methane, or liquid fuel such as kerosine andheavy oil is burned with auxiliary combustion gas, whereby the hotcombustion gas is produced. This hot combustion gas is mixed withauxiliary combustion gas, producing hot auxiliary combustion gas. Thishot auxiliary combustion gas is both mixed and burned with pulverizedsolid fuel such as pulverized coal as the main fuel within the maincombustion chamber defined at the front end portion of the burner,producing a stable flame having a temperature of about 2,000° to 2,400°C. It is possible to preheat the pulverized solid fuel to make the flameeven more stable if the main combustion chamber is spaced from theauxiliary combustion heater at an adequate distance.

As has been described, the burner according to the present invention hasan auxiliary combustion gas heater, and uses pulverized coal as its mainfuel. The effects of the invention are that a stable flame due tocombustion of pulverized solid fuel, the flame having a temperature of2,000° to 2,400° C., can be produced, and that energy cost is reducedand the size miniaturized, in contrast to combustion burners usinggaseous or liquid fuel mixed with pulverized solid fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is an axial-sectional view of a conventional combination burnerwhich uses pulverized coal mixed with liquid fuel;

FIG. 2 is an axial-sectional view of embodiment 1 according to oneaspect of the present invention;

FIGS. 3 to 8 show a hot oxygen lance according to another aspect of thepresent invention, wherein FIG. 3 is an axial-sectional view ofembodiment 2, FIG. 4 is an enlarged axial-sectional view of an oxygenheater in FIG. 3, FIG. 5 is an axial-sectional view of embodiment 3,FIG. 6 is an axial-sectional view of embodiment 4, FIG. 7 is an enlargedsectional view of an oxygen heater in FIG. 6, and FIG. 8 is a view takenalong the line VI--VI in FIG. 7; and

FIG. 9 is an axial-sectional view of a pulverized coal burner ofembodiment 5 according to still another aspect of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 2 shows an oxygen heater according to the first aspect of thepresent invention. In FIG. 2, reference numeral 1 designates the oxygenheater, and reference numeral 2 denotes an inner wall which forms theoxygen heater 1. This inner wall is made of such material asfireproofing material and metal. Reference numeral 3 designates acombustion chamber-defining member, 4 designates a combustion chamber, 5designates a fuel-supplying conduit, 6 denotes an oxygen-supplyingpassage, 7 denotes a nozzle for auxiliary combustion oxygen, 8 denotesan outlet for curtain oxygen, 9 designates an opening of the combustionchamber, 10 designates a flame and 11 denotes a chamber for mixingcombustion gas with curtain oxygen.

Also, reference letter a designates fuel, b designates oxygen, c denotesauxiliary combustion oxygen, d denotes curtain oxygen and e denotes aflow of hot oxygen containing combustion gas.

In this oxygen heater, the fuel-supplying conduit 5 is supplied with theliquid or gaseous fuel a, while the oxygen-supplying passage 6 issupplied with oxygen b. A part of the oxygen b is introduced into thecombustion chamber 4 through the nozzles 7 which are formed in thechamber-defining member 3 to communicate with both the combustionchamber 4 and the passage 6. The oxygen b is then mixed with the fuel awhich has also been introduced into the chamber 4 and the mixture of thefuel a and the oxygen b is burned. The burning mixture is then jettedout of the opening 9 and produces the flame 10. In the mixing process,the fuel and the oxygen are mixed extremely well and produce a stableflame since the nozzles 7 are oriented to direct the oxygen passingthrough the nozzles 7 in a path converging on the opening 9 and thecenter axis of the combustion chamber 4.

The other part of the oxygen gas (i.e., most of the oxygen gas) b isjetted out of the outlets 8, and forms the oxygen curtain d surroundingthe flame 10. This oxygen curtain absorbs the radiant heat generated bythe flame and hinders the heat by convection and conduction from beingtransferred to the inner wall 2, whereby the oxygen curtain prevents theinner wall 2 from being damaged. The curtain oxygen and the combustiongas produced by the flame 10 are mixed within the mixing chamber 11,resulting in the production of initial hot oxygen containing combustiongas having a levelled temperature distribution, which forms the hot gasflow e and is supplied to the place where it is demanded. As previouslydescribed, since the heater has a mixing chamber and there are producedin the heater a flame for heating oxygen and an oxygen flow to beheated, it is possible, by using this oxygen heater, to reduce the heatloss and thus to efficiently produce hot oxygen. Also for the samereason, the oxygen heater can be miniaturized.

Embodiment 2

FIG. 3 shows a hot oxygen lance according to the second aspect of thepresent invention. In FIG. 3, reference numeral 101 designates an outercylinder, and reference numeral 102 designates an oxygen heater disposedwithin the the outer cylinder 101. An enlarged axial-sectional view ofthe oxygen heater is shown in FIG. 4. Reference numeral 103 denotes acombustion chamber, 104 denotes a fuel-supplying conduit, 105 denotes anoxygen-supplying passage, 106 denotes nozzles for auxiliary combustionoxygen, 107 denotes nozzles for curtain oxygen, 107a denotes nozzles forouter curtain oxygen in the case that two oxygen curtains should beproduced, and 107b denotes nozzles for inner curtain oxygen. Referencenumeral 108 designates a hot oxygen gas-jetting nozzle, 109 designates aheat-insulating layer, 110 designates a jacket for cooling water, 111designates a partition inside the jacket 110, 112 designates a flame,113 designates a mixing chamber for mixing combustion gas and curtainoxygen, 114 designates a front end opening of the lance, and 115designates a furnace wall. Also, in FIGS. 3 and 4, arrow a means fuelflow, arrow b means oxygen flow, arrow c means flow of auxiliarycombustion oxygen, arrow d means curtain oxygen flow, arrow e means hotoxygen containing combustion gas flow, arrow f means feedwater flow andarrow g means drain flow.

The device illustrated in FIGS. 3 and 4 merely serves as a hot oxygenlance. This oxygen lance is provided at the center of the outer cylinder101 and behind the front end opening 114, with the oxygen heater 102which has the combustion chamber 103 and the nozzles 107. The combustionchamber 103 is provided for mixing the fuel with the oxygen and forburning the mixture. The nozzles 107 surround the combustion chamber 103to direct the oxygen flow passing therethrough to form an oxygencurtain. The heat-insulating layer 109 is disposed around the outercylinder 101, and the water jacket 110 is fitted around the nozzle 108and the front portion of the heat-insulating layer 109. Although, inFIG. 3, the heat-insulating layer 109 covers that portion of the outercylinder's outer face from the front end nearly to the periphery ofoxygen heater 102, it may cover only a portion of the outer cylinderfrom the position formed flame 112 to the mixing chamber 113. Althoughthe jacket 110 fits around that portion of the lance which is to bedisposed inside the furnace so that the lance is prevented from beingdamaged, it may fit around the entire lance. The jacket 110 shown inFIG. 3 is not the cooling means for the outer cylinder 101, therefore itwill be required to dispose a water cooling jacket 110 arround the outercylinder 101 instead of the heat-insulating layer 109 in order toprotect the outer cylinder 101 from the heat of the hot oxygen gas whenthe temperature of the hot oxygen gas exceeds 1,200° C.

Both the curtain oxygen nozzles 107 and the auxiliary combustion oxygennozzles 106 are supplied with oxygen through one passage, that is, theoxygen-supplying passage 105. The ratio between the amount of theauxiliary combustion oxygen and curtain oxygen depends on pressureresistance of the auxiliary oxygen nozzle 106. Naturally, there may bearranged two passages for supplying oxygen respectively to the nozzles106 and 107. Those oxygen may be supplied by two branched passagesbefore it was introduced into outer cylinder 101 of the lance, and thisarrangement is not preferred since it causes complications in theconstruction of the lance.

In this oxygen lance, the fuel-supplying conduit 104 is supplied withgaseous or liquid fuel a, and the oxygen-supplying passage 105 issupplied with oxygen gas b. A part of the oxygen gas b (i.e., arrow c)is introduced into the combustion chamber 103 through the auxiliarycombustion oxygen nozzles 106 and is mixed with the fuel a. This mixtureof the fuel a and the oxygen b is then burned and produces the flame112. When the fuel a is propane, the maximum temperature of the flame112 is approximately 2,700° C. On the other hand, the remainder of theoxygen b is introduced into the curtain oxygen nozzles 107 and, as shownby arrow d, is jetted out of the nozzles 107, forming a oxygen curtainbetween the outer cylinder 101 and the flame 112. This oxygen curtainreduces the heat transfer to the outer cylinder 101 to the smallestpossible degree. Next, within the mixing chamber 113, the curtain oxygenis mixed with the hot combustion gas generated due to the flame 112,resulting in the production of the hot oxygen containing combustion gas.This hot oxygen containing combustion gas is then, as shown by arrow e,discharged in a jet from the opening 114 of the nozzle 108 into thefurnace.

An oxygen heating test was carried out, in which the oxygen lancepreviously described was used with 0.30 Nm³ /h of fuel propane, 1.5 Nm³/h of auxiliary combustion oxygen and 25 Nm³ /h of curtain oxygen. As aresult, there was produced a hot oxygen containing combustion gas. Thetemperature and the oxygen content of the hot oxygen containingcombustion gas are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                        Curtain Oxygen (Nm.sup.3 /h)                                                                          25                                                    Fuel C.sub.3 H.sub.8 (Nm.sup.3 /h)                                                                    0.30                                                  Auxiliary Combustion Oxygen (Nm.sup.3 /h)                                                             1.5                                                   Oxygen Content of the Hot Gas (%)                                                                     92.3                                                  Temperature of the Hot Gas (°C.)                                                               800                                                   ______________________________________                                    

Embodiment 3

FIG. 5 shows another hot oxygen lance according to the second aspect ofthe present invention. In this lance, there are disposed not only abranch cylinder for supplying hot oxygen gas but also a center pipecoaxially within the outer cylinder in order to supply a furnace withpulverized material for refining such as, cokes, pulverized coal andiron ore. This center pipe may be a pipe for observing the inside of thefurnace instead of being the pulverized material-supplying pipe. Becausethe center pipe takes up the center position of the outer cylinder 101a,the outer cylinder 101a is provided with a branch cylinder in which theoxygen heater 102 is disposed. Although the branch cylinder 117 in FIG.5 is connected perpendicularly to the outer cylinder 101a, the anglebetween the outer cylinder and the branch cylinder may be set at random.

In FIG. 5, like reference characters as in FIG. 2 designatecorresponding parts, and descriptions of the corresponding parts areomitted. The reference numeral 101a denotes the main outer cylinder, 116denotes the center pipe, 117 denotes the branch cylinder, 109a denotes aheat-insulating layer for the main outer cylinder, 109b denotes aheat-insulating layer for the branch cylinder, and reference letter hdenotes a flow of the pulverized material for refining.

The functions of the branch pipe 117 and the oxygen heater 102 are thesame as that of the oxygen heater of embodiment 2. The pulverizedmaterial for refining is introduced into the center pipe 116 by acarrier gas such as carbon monoxide and argon, and is jetted from thenozzle 108 into the furnace together with hot oxygen containingcombustion gas.

Embodiment 4

FIG. 6 illustrates still another oxygen lance according to the secondaspect of the present invention. This lance is also used for supplyinghot oxygen and has a center pipe at the center of the lance. The centerpipe is also used either as a pipe for supplying the pulverized materialor as a pipe for observing the inside of the furnace. In the lance ofembodiment 3, the existence of the branch cylinder causes the entireconstruction of the lance to be complicated, whereby there arisesinconveniences such as difficulty in manufacturing the lance anddifficulty in operating the lance. In contrast, the lance of thisembodiment has both an oxygen heater 102a and a center pipe 116 which iscoaxially disposed in the outer cylinder 101. The oxygen heater 102a hasa plurality of combustion chambers defined around the center pipe 116.The heater 102a is provided with a plurality of oxygen nozzlesconsisting of small holes or slits, for directing oxygen passing throughthe nozzles to form an oxygen curtain enclosing the combustion chambers.

FIG. 7 is an enlarged axial-sectional view of the oxygen heater 102a.FIG. 8 is a view taken along the line VI--VI in FIG. 7. In thesedrawings, like reference characters as in embodiments 2 and 3 designatecorresponding parts, and descriptions of the corresponding parts areomitted. Reference numerals 103a_(l) to 103a_(n) designate thecombustion chambers, 104a_(l) to 104a_(n) designate conduits forsupplying the combustion chambers with fuel, 106a_(l) to 106a_(n)designate oxygen nozzles for introducing the auxiliary combustion oxygeninto the combustion chambers, and 107a_(l) to 107a_(n) denote oxygencurtain nozzles for directing oxygen passing therethrough to form theoxygen curtain enclosing the combustion chambers. In the same manner asembodiment 2, other oxygen nozzles forming another annular row ofnozzles may be provided around the annular row of the nozzles 107a_(l)to 107a_(n). Reference numerals 112a_(l) to 112a_(n) designate flamesproduced in the combustion chambers. Reference letter j designates anoxygen curtain formed between the outer cylinder 101 and the combustionchambers 103a_(l) to 103a_(n) by the oxygen jetted out of the curtainnozzles 107a_(l) to 107a_(n) , and reference letter k also designates anoxygen curtain formed between the center pipe 116 and the combustionchambers 103a_(l) to 103a_(n).

The fuel for the lance may be carried to the lance by a single passagewhich extends to the entrance of the outer cylinder 101 to connect withthe fuel-supplying conduits 104a_(l) to 104a_(n). Otherwise, the singlepassage extends into the outer cylinder 101 reaching in the vicinity ofthe oxygen heater 102a. The former single passage makes the constructionof the entire lance more complicated.

The oxygen may be introduced into the outer cylinder by means of aconduit and is distributed into the auxiliary combustion oxygen and thecurtain oxygen. The ratio between the amount of the auxiliary combustionoxygen and the amount of the curtain oxygen depends on the pressureresistance of both the nozzles 106a_(l) to 106a_(n) and the nozzles107a_(l) to 107a_(n). Each of the combustion chambers may have its ownoxygen-supplying conduit connected to the corresponding combustionchamber. However, such oxygen-supplying conduits are not preferred sincethey cause the construction of the lance to be complicated.

The functions of the lance having the oxygen heater of this embodimentare the same as that of the lance of embodiment 2. One additionalfunction of the lance of this embodiment is that the oxygen curtain k isformed between the center pipe 116 and the combustion chambers 103a_(l)to 103a_(n) as well as the oxygen curtain j between the outer cylinder101 and the combustion chambers. The oxygen curtain k prevents thecenter pipe 116 from being overheated.

Also, the lance of this embodiment has the merit that it is easier tomanufacture and to handle in comparison with the hot oxygen lance ofembodiment 3.

Table 2 shows the temperature and the oxygen content of a produced hotoxygen containing combustion gas when the lance of this embodiment haseight combustion chambers and is supplied with 0.35 Nm³ /h of fuelpropane, 1.75 Nm³ /h of auxiliary combustion oxygen and 25 Nm³ /h ofcurtain oxygen.

                  TABLE 2                                                         ______________________________________                                        Curtain Oxygen (Nm.sup.3 /h)                                                                          25                                                    Fuel C.sub.3 H.sub.8 (Nm.sup.3 /h)                                                                    0.35                                                  Auxiliary Combustion Oxygen (Nm.sup.3 /h)                                                             1.75                                                  Oxygen Content of the Hot Gas (%)                                                                     91.1                                                  Temperature of the Hot Gas (°C.)                                                               800                                                   ______________________________________                                    

Embodiment 5

FIG. 9 illustrates a pulverized coal burner according to the thirdaspect of the present invention. In this drawing, reference numeral 201denotes a burner body. 202 designates a pulverized coal-supplying pipe.203 denotes a conduit for supplying gaseous or liquid fuel for thepreheating of auxiliary combustion gas. 204 designates a branch pipe forsupplying gaseous or liquid fuel. Reference numerals 205a to 205n denotepipes for supplying gaseous or liquid fuel for the preheating ofauxiliary combustion gas. Reference numeral 206 designates an auxiliarycombustion gas-supplying conduit. 207 designates an auxiliary combustiongas supplying pipe. 208 denotes a passage defined by the pipes 202 and207 which are coaxial to each other. Reference numerals 209a to 209ndenote a plurality of auxiliary combustion gas heaters circumferentiallydisposed around the pulverized coal-supplying pipe 202. 210a to 210ndenote combustion chambers (the sub-combustion chamber) formed in theauxiliary combustion gas heaters. Reference numeral 211 denotes anauxiliary combustion gas nozzle for jetting auxiliary combustion gasinto the combustion chambers 210a to 210n. 212 denotes a flame forpreheating auxiliary combustion gas. 213 denotes a curtain nozzle forjetting auxiliary combustion gas so that the flow of auxiliarycombustion gas forms a auxiliary combustion gas curtain enclosing thecombustion chambers 210a to 210n. 214 denotes a mixing chamber formixing hot combustion gas with auxiliary combustion gas having roomtemperature. 215 denotes a member forming a pulverized coal combustionnozzle. Reference numerals 216a and 216b denote nozzles for jetting hotauxiliary combustion gas. 217 denotes a main combustion chamber. 218denotes a flame-throwing opening. 219 denotes a flame due to thecombustion of pulverized coal. The hot auxiliary combustion gas-jettingnozzles 216a and 216b consist of a plurality of small holes or slitsoriented to direct the auxiliary combustion gas passing therethrough ina path converging on points P and Q which are positioned on the centeraxis of the burner body 201 and in the vicinity of the opening 218.Naturally, other annular rows (3 or 4 rows) of the auxiliary combustiongas-jetting nozzles other than the nozzles 216a and 216b, may be formedin the nozzle-forming member 215.

Reference numeral 220 designates a heat-insulating layer disposed on theentire outer surface of auxiliary combustion-supplying pipe 207. Thisheat-insulating layer hinders heat generated by the auxiliary combustiongas heater 209a to 209n from being convectively transferred radiallyoutward.

Reference numeral 221 designates a cooling jacket for circulatingcooling water therein. This jacket 221 is provided to prevent the frontend portion of the burner, that is, mainly the forming member 215, frombeing damaged by the radiation heat radiated from the flame 219 and thefurnace.

Reference letter a denotes pulverized coal, b denotes auxiliarycombustion gas which may be comprised oxygen, oxygen-enriched air, orair, c denotes gaseous or liquid fuel, d denotes auxiliary combustiongas used for burning the fuel and preheating the curtain gas, e denotesauxiliary combustion gas used for forming the gas curtain, and f denotesa flow of hot auxiliary combustion gas.

In the aforementioned burner, pulverized coal, that is, the main fuel isintroduced into the pulverized coal supplying pipe 202 together with acarrier gas such as monoxide carbon and argon. On the other hand, thegaseous or liquid fuel for preheating the auxiliary combustion gas isintroduced into the gaseous or liquid fuel-supplying conduit 203, and issupplied into the gaseous or liquid fuel-supplying pipes 205a to 205nthrough the branch pipe 204. The gaseous or liquid fuel, then, reachesthe auxiliary combustion gas heaters 209a to 209n and is introduced intothe combustion chambers 210a to 210n. The auxiliary combustion gas isintroduced into the auxiliary combustion gas-supplying conduit 206, andreaches the auxiliary combustion gas heaters 209a to 209n via theauxiliary combustion gas supplying passage 208. A part of the auxiliarycombustion gas is, then, introduced into the combustion chambers 210a to210n through the auxiliary combustion gas nozzle 211. Subsequently, theauxiliary combustion gas introduced into the combustion chambers 210a to210n is mixed with the gaseous or liquid fuel which has been introducedinto the combustion chambers 210a to 210n. The mixture of the fuel andthe auxiliary combustion gas is then burned in the combustion chambers210a to 210n, whereby the flame 212 for preheating the auxiliarycombustion gas is produced. The other part of the auxiliary combustiongas passes through the curtain nozzles 213 and forms an auxiliarycombustion gas curtain enclosing the combustion chambers 210a to 210n.The gas curtain protects the auxiliary combustion gas-supplying pipe 207by hindering the heat from being convectively transferred from thepreheating flame 212 to the gas supplying pipe 207. The gas curtain alsominimizes the heat loss.

The preheating flames 212 formed in each combustion chamber 210a to 210nproduces hot combustion gas. This hot combustion gas is mixed with thecurtain gas within the mixing chamber 214, whereby hot auxiliarycombustion gas is produced. Then, this hot auxiliary combustion gas isintroduced into the nozzles 216a and 216b, and is jetted out of thenozzles 216a and 216b into the main combustion chamber 217. Thepulverized coal, which is introduced into the supplying pipe 202together with the carrier gas, is jetted into the main combustionchamber 217, and then, is mixed with the hot auxiliary combustion gashaving been jetted into the chamber 217. Then, the mixture of thepulverized coal and the hot auxiliary combustion gas at the same time asit is being burned, is jetted out of the opening 218, whereby the flame219 due to the combustion of the pulverized coal is produced. Since theauxiliary combustion gas introduced into the combustion chamber 217 ishot, the combustion in the chamber 217 continues in a stable manner,resulting in the production of a stable flame having a temperature ofapproximately 2,000° to 2,400° C.

Also, by setting the distance between the main combustion chamber 217and the auxiliary combustion gas heaters 209a to 209n at an adequatedistance, it is possible to preheat the pulverized coal in the supplyingpipe 202 by convectively transferring heat from the hot auxiliarycombustion gas to the pulverized coal via the pipe wall. This operationmakes it easier for the burner to produce a more stable flame.

What is claimed is:
 1. A hot oxygen lance comprising an outer cylinder,oxygen supply means for supplying oxygen to the inside of the outercylinder, andan oxygen heater and a center pipe, both disposed withinthe outer cylinder, the center pipe serving as a pipe for supplying apulverized material to the outer cylinder, the oxygen heater defining aplurality of combustion chambers communicating with the oxygen supplymeans and circumferencially disposed around the center pipe, for bothmixing and burning fuel with oxygen supplied thereto, each of thecombustion chambers having an opening for blowing a flame, the oxygenheater including: fuel supply means for supplying fuel to said pluralityof combustion chambers; and oxygen nozzles, surrounding the opening ofeach of said combustion chambers and communicating with the oxygensupply means, for allowing oxygen supplied thereto to flow out therefromand to form oxygen curtains, each of the curtains surrounding a flamedue to the combustion in the corresponding combustion chamber to protectboth the outer cylinder and the center pipe from heat emitted by theflame.
 2. A hot oxygen lance as recited in claim 1, wherein the oxygennozzles are arranged so that a multilayer of oxygen curtains are formed.3. A hot oxygen lance as recited in claim 2, wherein the oxygen nozzlesare arranged so that an inner oxygen curtain formed by the oxygenflowing out from the oxygen nozzles is of a flow rate higher than theflow rate of the outer adjoined oxygen curtain.
 4. A hot oxygen lance asrecited in claim 1, wherein the fuel is selected from the groupconsisting of gaseous fuel and liquid fuel.
 5. A hot oxygen lancecomprising an outer cylinder, a heat-insulating layer and/or a coolingjacket disposed around a part of or all of the outer surface of theouter cylinder, oxygen supply means for supplying oxygen to the insideof the outer cylinder, andan oxygen heater and a center pipe, bothdisposed within the outer cylinder, the center pipe serving as a pipefor supplying a pulverized material to the outer cylinder, the oxygenheater defining a plurality of combustion chambers, communicating withthe oxygen supply means and circumferentially disposed around the centerpipe, for both mixing and burning fuel with oxygen supplied thereto,each of the combustion chambers having an opening for blowing a flame,the oxygen heater including: fuel supply means for supplying fuel tosaid plurality of combustion chambers; and oxygen nozzles, surroundingthe opening of each of the combustion chambers and communicating withthe oxygen supply means, for allowing oxygen supplied thereto to flowout therefrom to form an oxygen curtain.
 6. A hot oxygen lance asrecited in claim 5, wherein the oxygen nozzles are arranged so that amultilayer of oxygen curtains are formed.
 7. A hot oxygen lance asrecited in claim 6, wherein the oxygen nozzles are arranged so that aninner oxygen curtain formed by the oxygen flowing out from the oxygennozzles is of a flow rate higher than the flow rate of the outeradjoined oxygen curtain.
 8. A hot oxygen lance as recited in claim 5,wherein the fuel is selected from the group consisting of gaseous fueland liquid fuel.
 9. In a pulverized solid fuel burner which includes:amember defining a main combustion chamber for both mixing and burning apulverized solid fuel with an auxiliary combustion gas; a pulverizedsolid fuel-supplying pipe, communicating with the main combustionchamber for leading the pulverized solid fuel into the main combustionchamber; and and auxiliary combustion gas-supplying pipe coaxial withand disposed around the solid fuel-supplying pipe and communicating withthe main combustion chamber, for leading the auxiliary combustion gasinto the main combustion chamber, the improvement which comprises anauxiliary combustion gas heater disposed within the auxiliary combustiongas-supplying pipe, the heater defining a sub-combustion chamber,communicating with the auxiliary combustion gas-supplying pipe, for bothmixing a burning gaseous or liquid fuel with auxiliary combustion gassupplied thereto, the sub-combustion chamber having an opening forblowing a flame, the heater including: fuel supply means for supplyingfuel to the sub-combustion chamber; and an oxygen nozzle, disposedaround the opening of the sub-combustion chamber and communicating withthe auxiliary combustion gas-supplying pipe, for allowing auxiliarycombustion gas, supplied thereto to flow out therefrom and to form a gascurtain, the gas curtain surrounding a flame due to the combustion inthe sub-combustion chamber to protect both the solid fuel-supplying pipeand the auxiliary combustion gas-supplying pipe from heat emitted by theflame.
 10. A pulverized solid fuel burner as recited in claim 9 whereinthe auxiliary combustion gas comprises oxygen.
 11. A pulverized solidfuel burner as recited in claim 9 wherein the auxiliary combustion gascomprises oxygen-enriched air.
 12. A pulverized solid fuel burner asrecited in claim 9 wherein the auxiliary combustion gas comprises air.